Office Memorandum: RPC Tech Note 5
SLAC, Power Conversion Department
March 20, 2001
To: Steve St Lorant MS 20
From: Martin Berndt MS 49
Subject: Reinstallation of 5 MW Power Supply at ESA
It appears that the old 70D43 magnet is destined to be used for some time in future ESA experiments. The 70D43 (the old LASS magnet) has aluminum coils designed for up to 6000 Amperes at 3.0 MW.
At this time the only way to energize this magnet will be by parallel operation of the two large PB202 and PB203 (nominally 1.75 MW each) power supplies located in Building 108. The following are some problems with this arrangement:
1.- Decreased reliability and increased complexity that results from parallel operation of two supplies.
2.- 6000 Amperes is an absolute maximum for the supplies. 5500 Amperes is a more realistic figure.
3.- The arrangement ties up the two large supplies in Building 108. If an additional dipole magnet requiring more than 240 Volts is needed for an experiment, it will be necessary to operate two of six existing 567 KW (actually capable of 650 KW each) power supplies, connected in series. This again adds complexity and decreases reliability.
It has been proposed to restore the old 5 MW power supply that was in Building 304, and install it outside ESA. With the removal of Building 304 now in process, the 5.0 MW power supply is being disassembled, and both the rectifier cabinet and transformer will be temporarily stored inside ESA. The power supply has a rating of 660 Volts at 7500 Amperes. By means of internal links it can also be configured for 330 Volts at 15000 Amperes.
The following is a preliminary cost estimate of the restoration and installation cost of the 5 MW supply outside ESA.
Description of Project
The proposal is for rebuilding the power supply for 660VDC, 7500 Amperes operation. The 330VDC, 15000 Ampere configuration will still be available through existing links, but will not be built into the controller at this time. If desired at some future date, an alteration of the controller will be necessary.
The SE corner outside ESA is the preferred location for the restored 5 MW power supply. This is where the old 5.8 MW supply was located in Building 114 (since removed). It is a good location, because: (a) Cooling water is available nearby, (b) a conduit for a 12KV service to the Research Area Substation is nearby, and (c) there is an existing trench and tunnel to house DC cabling to Building 108 and ESA.
Most of the cost figures for the 12KV high voltage installation are derived from conversations I had with Frank Brenkus.
1.- New 12KV 350Ampere service from the RA Sub to the SW corner of ESA. The old cable for the 5.8MW supply was removed and has to be replaced. Cost of installed cable: $100K.
2.- New switchgear cabinet for a 12KV safety disconnect and a vacuum contactor, with CTs and PTs. The old cabinets that were part of the 5 MW and the 5.8 MW supplies were removed and remodeled for use with the RF power supplies at PEPII. Cost of installed switchgear: $185K.
3.- Soil contamination remediation. There is soil contamination in the SW corner of ESA from old PCB transformer leaks. Soil will have to be removed and replaced. Estimated cost: $60K.
4.- New 10 x 10 leak-proof oil pit for 6MVA transformer, part of the 5MW supply.
Estimated cost: $25K.
5.- Transformer oil leak. One of the low voltage bushings has a small oil leak, and should be repaired. The transformer also should be tested, the oil dried, and replenished. Estimated cost: $10K.
6.- A 20 x 15 building on a raised concrete floor. Steel walls, except for a concrete block rear wall facing the transformer. Building to have a removable roof to permit lifting power supply cabinet into or out of the building. Cost for a 300 ft sq building at $250/sq ft: $75K.
7.- Repair and rework of secondary AC busses between the transformer and the rectifiers. These busses were mistakenly damaged (sawed off) during disassembly. Cost of repair: $5K.
8.- New large "hockey puck" style SCR assemblies to replace the many small units now in place, 24 SCRs total (2 SCRs / leg, 12 legs) instead of 132 small units, and 4 large "puck" style free-wheeling diodes. Estimated cost: $30K.
9.- New Zero Flux Transductor rated 8000 Amperes. This expense can be eliminated if it is possible to reuse a transductor from one of the unused SLC FF Triplets. Installed cost: $10K.
10.- Two new Enerpro SCR firing circuit assemblies, with slave drivers. Cost: $4K.
11.- New interlocks using existing SLAC designs based on solid state logic. Cost: $3K.
12.- New regulator, similar to existing designs used for PEPII. Cost: $3K.
13.- DC cabling from power supply to Building 108 cage. Assume 1" water cooled aluminum, 6 cables in parallel per leg. 3000 total cable, at $20/ft installed. Cost: $60K
14.- Miscellaneous items: Cost: $10K
15.- Engineering, design, and supervision. 400 hrs@ $75/hr. Cost: $30K
Total Cost $610K
Not cheap! The "big ticket" items are the 12KV service (items 1 & 2), and the building and site preparation (items 3, 4 & 5), which together add up to $445K. The rest, $165K, is for the restoration of a power supply that today would probably cost 2 million dollars to replace.
Dstribution: Pete Segura MS 49 Peter Bosted MS 44
Tony Donaldson MS 49 Steve Williams MS 75
John Beach MS 49
Dave Macnair MS 49
JJ Lipari MS 49